[Role of cAMP-dependent phosphorylation in passive transport of Ca2+ by myocardial sarcolemma].

: The myocardial sarcolemma vesicles loaded with Na2+ can accumulate Ca2+ against the concentration gradient in exchange for Na2+; the rate of this process is about 10 nmole of Ca2+ per mg of protein per min. The cAMP-dependent phosphorylation of sarcolemmal preparations has no effect on the Na+/Ca2+ exchange. At the same time the cAMP-dependent phosphorylation of protein components of the sarcolemma causes inhibition of the passive Ca2+ efflux from the vesicles depending on the degree of membrane phosphorylation.